Inrush current limiting icl ntc thermistors element14. Rated resistance r25 maximum permissible continuous current under rated operating conditions imax, dc or rms values for ac. Ntc thermistors for inrush current limiting b57234s0509m051 inrush current limiters icls s2345m51 data sheet ppd var pd 20160329 please read cautions and warnings and page 2 of 14 important notes at the end of this document. At ambient temperature the ntc device exhibits a high resistance, when the power is turnedon, the high resistance limits the amount of inrush current flowing into the circuit. The ntc thermistor is ideally suited for this application. Inrush current limiters b57364s0m0 icls s364 please read cautions and warnings and page 3 of 16 important notes at the end of this document. As shown in the figure below, limiting the inrush current of an smps by inserting an ntc thermistor is widely used as a way of making a lowcost and easy circuit for limiting inrush currents in power supplies. The most common method of inrush current protection is by using an ntc thermistor, so in this article, we will discuss more on ntc thermistor and how to use one to prevent inrush current in your designs. Ntc and ptc inrush current limiting thermistors rhopoint. Upon power up, an ntc ms32 100 15 thermistor has an initial resistance of 10 ohms. Use thermistors only in normal atmospheric conditions. Inrush current limiting icl ntc thermistors farnell israel. The device offers a short reset time, and as a ptc thermistor a quick reset will not result in a large inrush current, as its resistance is already at a high state.
B57153s0160m051 datasheet214 pages epcos ntc thermistors. Inrush current limiters b57364s0m0 icls s364 please read cautions and warnings and page 7 of 18. Ntc thermistors for inrush current limiting b57464s 400m inrush current limiters icls s46440m data sheet ppd var pd 20170731 please read cautions and warnings and page 2 of 12 important notes at the end of this document. Environmental conditions must not harm the thermistors. Inrush current limiters b57236s0m0 icls s236 please read cautions and warnings and page 9 of 20. Ptc thermistors for inrush current limiting ametherm. Inrush ptc thermistor ametherm inrush current limiters. Application note how to use ntc thermistors for inrush current limiting. To limit inrush current, an ntc thermistor is placed between the power supply. Strict conditions of mixing, pressing, sintering and metallization ensure an excellent batchtobatch product characteristics. When mounting ntc thermistors you have to ensure that there is an adequate distance. St series inrush current limiting power thermistors. An inrush current limiter is a component used to limit inrush current to avoid gradual damage to components and avoid blowing fuses or tripping circuit breakers. How to use ptc thermistors as current protection tech.
Ntc thermistors can be used as inrushcurrent limiting devices in power. When mounting ntc thermistors you have to ensure that there is an adequate distance between the thermistor and all parts which are sensitive to heat or combustible. Ntc thermistors are used as icls inrush current limiters to protect circuits of electrical and electronic devices against inrush currents easily and effectively. The capacitor ctest is discharged via the series resistor rs and the ntc inrush current limiter. Ntc thermistors general characteristics 1 introduction ntc thermistors are thermally sensitive resistors made from a mixture of mn, ni, co, cu, fe oxides. Inrush current limiting icl ntc thermistors newark. Inrush current limiting icl ntc thermistors farnell uk. Choosing ntc thermistor for inrush current limiting. Many of ametherms inrush current limiters have ul andor csa recognition and are available worldwide from our distribution partners and direct from our manufacturing facility in carson. The diverse product range not only includes different shapes smd chip and lead types, but also covers diverse applications such as inrush current suppression and temperature compensation. Applicationsswitchmode power suppliessoftstart motors, e. Inrush current limiters b57238s0m0 icls s238 please read cautions and warnings and page 4 of 18 important notes at the end of this document. The circuit usually relies on the ntc thermistor heating up due to the current passing through it.
Littelfuse power thermistors are suitable for suppressing high inrush currents in switching power supplies and other applications where the high initial starting currents are undesirable. Inrush current limiter an ntc disc thermistor subjected to a change in power will experience a time lag before reaching a lower resistance. Instead of passing 100 a, the ntc ms32 100 15 only allows 35 a to pass through. It limits surge current by functioning as a power resistor which drops from a high cold resistance to a low hot resistance when heated by the current flowing through it. Inrush current limiters b57364s0m0 icls s364 please read cautions and warnings and page 8 of 20. Ntc thermistors for inrush current limiting, leaded and. As the inrush current drops, the ntc thermistor selfheats and its resistance drops to a low enough value to pass current through. At this vrms, and to block 30a of peak inrush current 10 ohms ntc is required. The capacitor c test is discharged via the series resistor r s and the ntc inrush current limiter.
This article describes various example applications of these products, used for icl inrush current limiting purposes to easily and effectively suppress inrush current. Inrush current limiting icl ntc thermistors at element14. Sintered ceramic bodies of various sizes can be obtained. It must be ensured that no water enters the ntc thermistor e. Inrush current limiters b57364s0m0 icls s364 please read cautions and warnings and page 4 of 20 important notes at the end of this document. How to use ntc thermistors for inrush current limiting changpuak. Application ntc thermistor for inrush current limiting in peripheral communication equipment, e. How do you choose the right type of ntc thermistor to limit. The complete application note can be downloaded from. This presentation will focus on the following topics.
Inrush current limiter circuit using ntc thermistor. Negative temperature coefficient ntc thermistors and fixed resistors are often used to limit inrush current. Tdk has an extensive lineup of inrush current limiting ntc thermistors available. Limiting inrush current with ntc and ptc thermistors. B57237s0109m0 datasheet214 pages epcos ntc thermistors. Ametherm ntc, ptc and inrush current limiting thermistors at rhopoint components. Ppd var pd 20170731 please read cautions and warnings and page 4 of 12. They suppress the high inrush current surges occurring in cases such as the charging of lowimpedance smoothing capacitors. How do you choose the right type of ntc thermistor to limit inrush current for capacitive applications. Like all ntcs, ntc thermistors for inrush current limiting are made of polycrystalline mixedoxide ceramics. Inrush current limiting power thermistors temperature. One of the properties of ptc thermistors is that when an excessively large current flows, they generate heat by themselves and become highly resistive.
The method uses negative temperature coefficient ntc resistor connected in series with the power input line. Ntc thermistors for inrush current limiting, as all ntcs, are made of polycrystalline mixed oxide ceramics. Inrush current limiters b572p009m31 icls p please read cautions and warnings and page 3 of 14 important notes at the end of this document. Ametherm inrush current limiters and ntc thermistors have been made in the usa since 1994. There are 3 major criteria for selecting the best ntc thermistor inrush current limiter, surge suppressor for an application. Inrush current limiters b57153s0m0 icls s153 please read cautions and warnings and page 3 of 16 important notes at the end of this document. Jameco will remove tariff surcharges for online orders on instock items learn more. Ntc thermistors for inrush current limiting b57464s 400m inrush current limiters icls s46440m. I have some trouble with choosing an ntc to limit the inrush current, where i want to bypass the ntc with a relay after a certain time. Inrush current limiters b57364s0m0 icls s364 please read cautions and warnings and page 8. Inrush current limiters b57238s0m0 icls s238 please read cautions and warnings and page 4 of 20 important notes at the end of this document. Ntc inrush current limiters, selection guide author.
This article describes applications for inrush current limiting, overcurrent protection and telecom application. Applications based on current time characteristic are. This time lag can be utilized to limit the inrush surge current the larger the part, the greater the lag. Inrush current limiters b57236s0m0 icls s236 please read cautions and warnings and page 9 of 21. Nov 02, 2015 presentation overview today were going to cover how to improve inrush current protection using ntcbased limiting and ptcbased limiting. Thermometrics current limiters ntc inrush cl series. Ntc thermistors for inrush current limiting pdffile. E209153, the devices are the industrys only inrush current limiters certified to ul 1434 for. Internal construction the above picture shows the internal construction of epcos icls. Inrush current limiters b57464s0m000 icls s464 please read cautions and warnings and page 3 of 18 important notes at the end of this document. For example, consider a system with 10 a continuous current and an inrush current of 100 a.
Inrush current limiters b57211p0m31 icls p11 please read cautions and warnings and page 9 of 21. Ntc thermistors for inrush current limiting, leaded. Rohs2certified inrush current limiters, ntc thermistors. Testing of ntc inrush current limiter circuit to evaluate the effect of the inrush current a capacitive load is connected across a power supply unit. Littelfuse inrush current limiters power thermistors are specially formulated and processed ntc thermistors suitable for suppressing high inrush currents in switching power supplies and other applications where the high initial starting currents are undesirable. Inrush current limiters b57236s0m0 icls s236 please read cautions and warnings and page 3 of 14 important notes at the end of this document. Murata ntc thermistors employ elements featuring high precision and good thermal response. Inrush current limiting icl ntc thermistors product list at newark. With its industryhigh voltage rating, ametherms mcl20 500100a can withstand hundreds of hits of maximum inrush current without degrading.
Ametherms broad line of ntc thermistors for inrush current limiting applications these inrush current limiters can be used in circuits of up to 480 vac. After a short time, the ntc thermistor resistance decreases to a low value due to self heating and does not affect normal operation. Ntc thermistors for inrush current limiting leaded and coated. Sep 22, 2016 how to select ntc thermistors for inrush current limiting. They suppress high inrush current surges, which occur. Upon power on, the ntc thermistor provides high resistance to limit inrush current. Vntc voltage drop across the ntc under test v the capacitor ctest is discharged via the series resistor rs and the ntc inrush current limiter. Ntc thermistors for inrush current limiting b57364 s0121m000 inrush current limiters icls s364120m data sheet ppd var pd 20160111 please read cautions and warnings and page 2 of 12 important notes at the end of this document. The same result can be achieved even when the ntc thermistor is connected after the rectifier circuit. In the dc power circuit of a dcdc converter or the like, an ntc thermistor is used as a power thermistor and effectively limits an inrush current, with which the input and output capacitors are charged at the time of powering on.
Ntc thermistors for inrush current limiting leaded and. Some of the factors to consider when designing ntc thermistor as an inrush current limiter are. Use thermistors only within the specified voltage and current ranges icls. If connected in parallel, the ntc thermistor with the smallest rated resistance consumes almost the entire current in the circuit and the resulting overload could destroy the component. Thermometrics cl series of inrush current limiting thermistors consists of a disc thermistor with uninsulated leadwires, and are used to control inrush current when switching power supplies. There are 3 major criteria for selecting the best ntc thermistor inrush current limiter, surge suppressor for an application rated resistance r25 maximum permissible continuous current under rated operating conditions imax, dc or rms values for ac. Thermistors, or thermallysensitive resistors are resistors whose resistance depends on temperature and can therefore be used for temperature measurement and regulation in a circuit or to react to a temperature change. These characteristics are related to the heat capacity and dissipation constant of the ntc thermistor used. Inrush current limiters b57153s0m0 icls s153 please read cautions and warnings and page 3 of 14 important notes at the end of this document.
How to select ntc thermistors for inrush current limiting. How to use ntc thermistors for inrush current limiting tech. Fluid level applications the thermistor can be used to sense the presence or absence. Inrush current limiting icl ntc thermistors at farnell. Contact of ntc thermistors with any liquids and solvents should be prevented. Ntc thermistors for inrush current limiting b57127p0xxxm301 inrush current limiters icls p27 preliminary data ppd var pd 20150622 please read cautions and warnings and page 4 of 5 important notes at the end of this document. To limit inrush current, an ntc thermistor is placed between the power supply and system see figure 1.
Competitive prices from the leading inrush current limiting icl ntc thermistors distributor. Insidepenton com electronic design adobe pdf logo tiny, download this. Capacitive applications ametherm the purpose of this module is to introduce and elaborate on factors determining the selection of ntc thermistors for inrush current limiting on capacitive applications, demonstrate how the calculations are done for each factor in an example, and recommend a part. Limit inrush current in industrial and commercial power products with ntc or ptc thermistors. Please read cautions and warnings and page 4 of 20 important notes at the end of this document. Matt cuhadar from the ametherm team answers a reader question about choosing the right type of ntc thermistor to limit inrush current for capacitive applications. Their unique design enables them to handle extremely high current and voltage levels. With this property, they are used as overcurrent protection devices. The main purpose of limiting inrush current is to prevent components in series with the input to the dcdc convertor from being damaged. The resistance of negative temperature coefficient. In general, inrush current limiters need time to return to their cold state in which they can provide adequate inrush current limiting due to their high.